The long-term goal of the proposed research is to better understand the perceptual effects of electrode configuration in cochlear implants (CIs). Various electrode configurations (i.e., stimulation modes) are possible in CI devices, e.g., monopolar (MP), bipolar (BP), etc. Currently, a fixed stimulation mode (commonly MP) is used for clinical fitting. Preliminary studies show that different stimulation modes can elicit distinct sound percepts, possibly due to the differences in the spread of excitation, suggesting that perceptual spectral patterns provided by MP or BP modes may be quite different. Combined MP and BP stimulation (i.e., "combined-mode") may provide an advantage over a fixed, single stimulation mode by providing information that is not available in an MP-only mode. In the proposed study, we will examine whether a combined-mode processor can improve CI users'speech recognition (effects of extended practice with the new map will also be studied), and determine if sound source segregation is improved with combined-mode presentation (in the context of psychophysics and multiple speech sounds). In addition, pitch relations between MP and BP stimulation will be objectively assessed in an auditory stream segregation experiment. Taken together, the results of the proposed experiments may lead to improved speech processing strategies without requiring substantial modifications to current systems, as combined-mode processors may provide a greater number of perceptual channels within the fixed number of implanted electrodes, and thus greatly benefit both current and future CI users. Taken together, the results of the proposed experiments could lead to improved hearing in CI users without requiring substantial modifications to current systems and benefit both current and future CI users. PUBLIC HEALTH RELEVANCE: The proposed study examines how deaf patients who have received cochlear implants perceptually organize one sound or multiple sounds with the electrical currents from the device. By investigating a new method of constructing current channels in a cochlear implant system that facilitates a good hearing and understanding of sounds, more benefits from the device will be expected in the future.